1. Field of the Invention
The present invention relates to a run-flat tire in which run-flat durability can be improved while maintaining the ride comfort and drainage performance.
2. Description of the Related Art
In recent years, a run-flat tire with a pair of reinforced sidewall portions is well known. Typically, such a run-flat tire is provided with a reinforcing rubber layer with a crescent shape in each sidewall portion. In order to improve durability of the run-flat tire, it is proposed to increase rigidity of the reinforcing rubber layer so as to reduce the tire flexure during run-flat running.
Generally, when the run-flat tire is being installed in a vehicle, an inboard sidewall portion thereof is difficult to obtain cooling effect during running compared to the outboard sidewall portion which faces on a street side. Accordingly, the reinforcing rubber layer disposed in the inboard sidewall portion of the tire tends to soften in the heat generation, and thereby the run-flat tire tends to be damaged in the inboard portion due to the large tire flexure in the inboard sidewall portion.
In order to prevent the large tire flexure in the run-flat tire during run-flat running, reinforcing rubber layers with still higher rigidity may be employed in sidewall portions. However, such a run-flat tire tends to deteriorate ride comfort.
It is an object of the present invention to provide a run-flat tire in which run-flat durability can be improved while maintaining the ride comfort as well as drainage performance.